MybatisPlus使用教程

参考文档:https://www.jianshu.com/p/12ec123d20e8
https://www.jianshu.com/p/12ec123d20e8

导入依赖包

<dependencies>
        
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
            <version>2.3.1.RELEASEversion>
        dependency>
        
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <scope>runtimescope>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintagegroupId>
                    <artifactId>junit-vintage-engineartifactId>
                exclusion>
            exclusions>
        dependency>
        
        <dependency>
            <groupId>com.baomidougroupId>
            <artifactId>mybatis-plus-boot-starterartifactId>
            <version>3.1.2version>
        dependency>
        
        <dependency>
            <groupId>com.alibabagroupId>
            <artifactId>druidartifactId>
            <version>1.1.0version>
        dependency>
    dependencies>

项目结构

springboot配置文件

spring:
  datasource:
    # 设置数据源类型为阿里巴巴Druid数据源
    type: com.alibaba.druid.pool.DruidDataSource
    # 数据库驱动
    driver-class-name: com.mysql.cj.jdbc.Driver
    # mysql数据库连接地址,時區為本地時區，支持Unicode編碼，使用UTF-8編碼,serverTimezone=UTC解决时区报错
    url: jdbc:mysql://39.97.68.32:3306/mybatisplus?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8
    # mysql用户名
    username: root
    password: root123

    # 數據源初始連接數
    initialSize: 5
    # 最小空閒數
    minIdle: 5
    # 最大活躍數
    maxActive: 20
    # 配置連接超時時間
    maxWait: 60000
    timeBetweenEvictionRunsMills: 60000
    minEvictableIdleTimeMills: 300000
    validationQuery: SELECT 1 FROM DUAL
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true

    # 配置后，druid控制台才能監控sql語句執行
    # 配置监控统计拦截的filters, stat:监控统计  log4j:日志记录  wall:防御sql注入
    filters: stat,wall,log4j
    maxPoolPreparedStatementPerConnectionSize: 20
    userGlobalDataSourceStat: true
    connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMilils=500
mybatis:
  type-aliases-package: com.liwi.springbootmybatisplus.pojo
  mapper-locations: classpath:mapper/*.xml

创建Mapper映射文件

使用mybatisplus框架时必须继承内部提供的 BaseMapper类,其中范型为与数据库进行映射的Pojo对象. mybatisplus提供了许多简单的增删改查操作.
UserMapper.class

package com.liwi.springbootmybatisplus.mapper;


import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.liwi.springbootmybatisplus.pojo.User;
import org.springframework.stereotype.Repository;

//
@Repository
public interface UserMapper extends BaseMapper<User> {

}

测试对user表插入一条数据

test.class

package com.liwi.springbootmybatisplus;

import com.liwi.springbootmybatisplus.mapper.OrderMapper;
import com.liwi.springbootmybatisplus.mapper.UserMapper;
import com.liwi.springbootmybatisplus.pojo.Order;
import com.liwi.springbootmybatisplus.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.Date;

@SpringBootTest
class SpringbootMybatisplusApplicationTests {

    @Autowired
    UserMapper userMapper;

    @Test
    void contextLoads() {
        User user = new User();
        user.setName("lindan");
        user.setAge(32);
        user.setCreate_time(new Date());
        user.setEmail("[email protected]");
        userMapper.insert(user);

    }
 }

常用注解

MyBatisPlus提供了一些注解供我们在实体类和表信息出现不对应的时候使用。通过使用注解完成逻辑上匹配。

注解名称	说明
@TableName	实体类的类名和数据库表名不一致时
@TableId	实体类的主键名称和表中主键名称不一致
@TableField	实体类中的成员名称和表中字段名称不一致

演示

package com.liwi.springbootmybatisplus.pojo;

import com.baomidou.mybatisplus.annotation.TableName;

import java.util.Date;

// 将该对象与t_user表进行映射
@TableName("t_user")
public class User {
    private Long id;
    private String name;
    private int age;
    private String email;
    private Long manager_id;
    private Date create_time;
}

主键策略

// @TableId(value=,type=)
package com.baomidou.mybatisplus.annotation;

public enum IdType {
    AUTO(0), //自增(数据库也要自增)
    NONE(1), //未设置主键时
    INPUT(2), //手动输入
    ID_WORKER(3),  //默认额全局唯一ID
    UUID(4),	//默认额全局唯一ID
    ID_WORKER_STR(5);  //ID_WORKER的字符串表示法

    private final int key;

    private IdType(int key) {
        this.key = key;
    }

    public int getKey() {
        return this.key;
    }
}

配置一个乐观锁

当每次对数据进行更新的时候,会比对version值是否与缓存中的version一致,一致则更新
1.在Pojo对象中加入version属性,添加@Version注解
2.数据库对应关系表添加version字段
3.创建MybatisPlusCnfig.class配置类
MybatisPlusCnfig.class

package com.liwi.springbootmybatisplus.config;
import com.baomidou.mybatisplus.extension.plugins.OptimisticLockerInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@MapperScan("com.liwi.springbootmybatisplus.mapper")
@EnableTransactionManagement
@Configuration
public class MybatisPlusConfig {

    // 注册乐观锁插件
    @Bean
    public OptimisticLockerInterceptor optimisticLockerInterceptor(){
        return new OptimisticLockerInterceptor();
    }
}

测试代码

    @Test
    void testOptimistic(){
        User user = userMapper.selectById(1);
        System.out.println(user);
        user.setCreate_time(new Date());
        userMapper.updateById(user);
    }

结果sql中带上了version字段进行条件判断

分页

1. sql语句中limit实现
2. 使用pageHelper插件进行实现
3. MybatisPlus自带的分页插件(需要配置拦截器实现)

package com.liwi.springbootmybatisplus.config;


import com.baomidou.mybatisplus.extension.plugins.OptimisticLockerInterceptor;
import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@MapperScan("com.liwi.springbootmybatisplus.mapper")
@EnableTransactionManagement
@Configuration
public class MybatisPlusConfig {
    // 分页插件
    @Bean
    public PaginationInterceptor paginationInterceptor(){
        return new PaginationInterceptor();
    }
}

测试代码

// 使用分页插件进行分页查询
    @Test
    void testSelectPage(){
        // 从第0条数据开始,每页5条数据
        Page page = new Page(0,5);
        userMapper.selectPage(page,null);
        List<User> users = page.getRecords();
        users.forEach(System.out::println);
        page.getRecords().forEach(System.out::println);

    }

逻辑删除

物理删除: 从数据库直接删除数据
逻辑删除: 设置一个字段deleted =0 ,当进行删除时对修改deleted = 1,这样可以让管理员能查看到被删除的记录

1. 在数据库与Pojo对象添加deleted字段,pojo加上@TableLogic注解
2. 在mybatisplusConfig配置文件中添加插件
3. application.yaml配置deleted值 或 注解配置mybatisplus版本须大于3.2
   application.yaml

mybatis-plus:
  global-config:
    db-config:
      # 删除表示1
      logic-delete-value: 1
      # 未删除时表示0
      logic-not-delete-value: 0

@TableLogic(value = "1",delval = "0")  //逻辑删除
   private Integer showStatus;

插件导入

package com.liwi.springbootmybatisplus.config;
import com.baomidou.mybatisplus.core.injector.ISqlInjector;
import com.baomidou.mybatisplus.extension.injector.LogicSqlInjector;
import com.baomidou.mybatisplus.extension.plugins.OptimisticLockerInterceptor;
import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.transaction.annotation.EnableTransactionManagement;
@MapperScan("com.liwi.springbootmybatisplus.mapper")
@EnableTransactionManagement
@Configuration
public class MybatisPlusConfig {
	// 删除插件(过时了)
    @Bean
    public ISqlInjector sqlInjector(){
        return new LogicSqlInjector();
    }
}

测试

 @Test
    void testDelete(){
        // 删除id=4的几率
        userMapper.deleteById(4);
    }

结果:执行deleteById方法,deleted值被修改(并没真正删除记录)
注意:在执行selectById(id)方法时,会自动过滤deleted值为1 的记录

性能检测

用于检测sql执行时的性能如何

1. 添加插件

package com.liwi.springbootmybatisplus.config;
import com.baomidou.mybatisplus.core.injector.ISqlInjector;
import com.baomidou.mybatisplus.extension.injector.LogicSqlInjector;
import com.baomidou.mybatisplus.extension.plugins.OptimisticLockerInterceptor;
import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import com.baomidou.mybatisplus.extension.plugins.PerformanceInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Profile;
import org.springframework.transaction.annotation.EnableTransactionManagement;
@MapperScan("com.liwi.springbootmybatisplus.mapper")
@EnableTransactionManagement
@Configuration
public class MybatisPlusConfig {
    // 性能检测插件
    @Bean
    @Profile({"dev"})
    public PerformanceInterceptor performanceInterceptor(){
        PerformanceInterceptor p = new PerformanceInterceptor();
        p.setMaxTime(1);  // 设置sql执行最大时间ms,超出时间不执行sql报错
        p.setFormat(true);  // 是否格式化sql输出
        return p;
    }
}